Multi-parametric fit method in reconstruction of brachytherapy needles

Abstract

PurposeTo adapt the multi-parametric fit method to reconstruct brachytherapy needles inserted with free hand technique for treatment of surface malignancies. MethodsAn alternative reconstruction method for brachytherapy (BT) needles is presented. The method is based on the digitized tip and end coordinates on pairs of posterior-anterior and posterior-oblique reconstruction images obtained with a non-isocentric C-arm. The needles tip and end coordinates are computed with the multi-parametric fit method that also incorporates the determination of the magnification factors of the reconstruction images. We tested the reconstruction accuracy with radio-opaque markers inserted into known positions. The range of C-arm angles that resulted in an accurate reconstruction was also investigated. We applied the method in treatments of the vulvar cancer using 3 to 5 pieces of BT needles located in a distance of approximately 1 cm. ResultsThe phantom test showed largest difference between the reconstructed and expected distance between the simulated needles ±1.3 mm. In vulvar insertions, the reconstructed position of the BT needles obtained with different image pairs agreed within 3 mm. ConclusionThe reconstruction accuracy of the multi-parametric fit method in with proper imaging is suitable for the clinical use.